This photograph shows how much better soap is than hand sanitizer

It can be hard to change the way you've been doing something for your whole life.

But with widespread concern about the spread of the coronavirus, it's a challenge many people face.

All of us (hopefully) wash our hands daily, and yet it's rare to see somebody standing at the sink next to you do a full 20- to 30-second lather and scrub, as we're now all being advised to do by health officials.

If you're finding it challenging to get into the habit of washing for longer, the actress Kristen Bell has some inspiration for you.

Bell posted a series of photos on Instagram that her mom had sent her, showing her hands at different stages of cleanliness.

Using a UV light and a cream called Glo-Germ — a mineral oil that simulates germs, and is only visible under a UV light — she was able to capture how much dirt was on her hands, even though they seemed clean to the naked eye.

It showed a dramatic difference between the potency of a six-second wash with soap and a 15-second wash with soap.

Though more similar, there was also a marked difference between a 15-second wash with soap and a 30-second one: After 15 seconds, Bell's mom still had some stubborn traces of bacteria stuck in the wrinkles of her fingers and her knuckles, which faded after a 30-second scrub.

We did the same experiment comparing a soapy hand-wash with hand sanitizer

Last week, Business Insider conducted a similar experiment, comparing hand sanitizer and a thorough hand-wash.

Health officials agree that it's a good idea for everyone to use hand sanitizer, particularly those with underlying conditions like asthma or emphysema, but urge people not to view it as a replacement for soap and water.

As we found with our own experiment, hand sanitizer is effective, but nowhere near as effective as hand-washing.

I put on Glo-Germ and got a UV-lit photo taken of my dirty hand after I'd gone to the pharmacy to buy some household items, using cash and also touching a keypad to type in my rewards card number. As you can see, they were quite dirty.

Then, I put on a liberal dose of Purell hand sanitizer. (In order to make sure hand sanitizer does its temporary job, you need almost a teaspoon of it, according to the American Council on Science and Health.)

With that, the germs cleared up quite a bit. However, hand sanitizer does not remove bacteria (as hand soap does). It simply neutralizes the bacteria, but leaves it on your hand, allowing it to resurge later.

The most striking photo was the final one, after I lathered my hands for 20 seconds and rinsed for five to 10 seconds. It's the photo that glows the least, because there are so few germs for the Glo-Germ to cling to.

There is a hand-washing gender gap

Research has long-shown that hand-washing isn't a given for everyone.

An international study in 2014, led by UK researchers, found 19% of people wash their hands with soap after coming into contact with feces.

Health officials insist it's imperative we turn those numbers around — according to recent research by MIT increasing hand-washing at just 10 airports in the US would reduce the spread of the coronavirus by 60 percent.

And yet, Insider Data conducted a poll last month which found that while many people are washing their hands more, there is a significant gender gap: of the 1,000 people surveyed, 65% of women said they were taking more care to wash their hands, compared to 52% of men.

Wash and scrub your hands for 20 seconds — and if you don't like singing "Happy Birthday," try "Jolene"

A useful way to keep your hand-washing on track is to sing a song in your head (or out loud), and only stopping when you've finished.

The classic is to sing "Happy Birthday" twice. But on Monday, Insider compiled a list of other songs you can scrub to, including "Jolene" and "Raspberry Beret."

And remember, even after the song is over, take the time to dry your hands thoroughly — new germs flourish in moisture.